Introduction: Uniflow 🦄- Simple Unidirectionnel Data Flow for Android & Kotlin, using Kotlin coroutines and open to functional programming
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Current version is 0.8.9

Choose one of the following dependency:


// Minimal Core
implementation 'io.uniflow:uniflow-core:$version'
testImplementation 'io.uniflow:uniflow-test:$version'

// Android
implementation 'io.uniflow:uniflow-android:$version'
testImplementation 'io.uniflow:uniflow-android-test:$version'

// AndroidX
implementation 'io.uniflow:uniflow-androidx:$version'
testImplementation 'io.uniflow:uniflow-androidx-test:$version'

this version is based on Kotlin 1.3.50 & Coroutines 1.3.0

Web Article 🎉

Full documentation 📖

Chat on Slack 💬

Come talk on Kotlin Slack @ #uniflow channel

Quick intro 🚸

UniFlow help you write your app with a simple unidirectional data flow approach (think states and events) to ensure consistency through the time, and this with Kotlin Coroutines.

UniFlow provides:

  • Smart way to write a Data flow in pure Kotlin
  • Android extensions to let you just focus on States & Events
  • Ready for Kotlin coroutines
  • Easy to test
  • Open to functional programming with Arrow
What is Unidirectional Data Flow? 🤔

### What is Unidirectional Data Flow? Unidirectional Data Flow is a concept that means that data has one, and only one, way to be transferred to other parts of the application. This means that: - state is passed to the view - actions are triggered by the view - actions can update the state - the state change is passed to the view The view is a result of the application state. State can only change when actions happen. When actions happen, the state is updated. Thanks to one-way bindings, data cannot flow in the opposite way (as would happen with two-way bindings, for example), and this has some key advantages: it’s less error prone, as you have more control over your data it’s easier to debug, as you know what is coming from where

Getting Started 🚀

Writing your first UI state

Describe your data flow states with UIState:

data class WeatherState(val day : String, val temperature : String) : UIState()

Publish state updates from your ViewModel:

class WeatherDataFlow(val repo : WeatherRepository) : AndroidDataFlow() {

    fun getWeather() = setState {
        // call to get data
        val weather = repo.getWeatherForToday().await()
        // return a new state
        WeatherState(weather.day, weather.temperature)

Observe your state flow from your Activity or Fragment:

class WeatherActivity : AppCompatActivity {

    val weatherFlow : WeatherDataFlow ... // ViewModel created with Koin for example :)

    override fun onCreate(savedInstanceState: Bundle?) {        
        // Observe incoming states
        onStates(weatherFlow) { state ->
            when (state) {
                // react on WeatherState update
                is WeatherState -> showWeather(state)

Easy to test!

Create your ViewModel instance and mock your states observer:

val mockedRepo : WeatherRepository = mockk(relaxed = true)
lateinit var dataFlow : WeatherDataFlow

fun before() {
    // create WeatherDataFlow instance with mocked WeatherRepository
    dataFlow = WeatherDataFlow(mockedRepo)
    // create mocked observer
    view = detailViewModel.mockObservers()

Now you can test incoming states with hasState. We are providing Mockk to help mock underlying coroutines call:

fun `has some weather`() {
    // prepare test data
    val weatherData = WeatherData(...)
    // setup mocked call
    coEvery { mockedRepo.getWeatherForToday() } return weatherData

    // Call getWeather()

    // verify state
    verifySequence {
        view.hasState(WeatherState(weatherData.day, weatherData.temperature))

Want to see more?

Documentation can be found here

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